ABSTRACT
The mechanistic—empirical approach for pavement design was recently adopted by the Association of State Highway and Transportation Officials (AASHTO), but this method has not been fully implemented by many state agencies. In fact, over half of the departments of transportation in the U.S. currently use some form of the older empirical AASHTO method and many are years away from adopting the new design approach. Therefore, it is critical to continue to refine the empirical AASHTO Design Guide methodology to ensure its results are optimized for everyday design practice. Previously, a study was conducted using measured performance data from the National Center for Asphalt Technology (NCAT) Test Track to recalibrate the asphalt layer coefficient (a1). In this earlier study, conventional asphalt materials constructed within full-scale test sections were analyzed and a new value of 0.54 was computed and implemented by the Alabama Department of Transportation (ALDOT). This study is a continuation of the previous research, but focuses on more innovative and sustainable materials that contain higher Reclaimed Asphalt Pavement (RAP) contents, warm mix technologies (foaming and additives) and an open-graded friction course. The data from these six sections were analyzed and the recalibrated structural coefficient was 0.55. Statistical testing indicated no statistical difference from the previous study where 0.54 was determined. This study is a key validation of the earlier work and supports the continued use of 0.54 to ensure optimized pavement designs using these sustainable materials.
